I. Introduction
A Electronic devices working in the Terahertz needs extremely high cutoff frequency ft. InP HEMT and InP HBT, representing the fastest transistors were reported with ft around 1THz. the frequency performance of transistors had hardly improved over 1THz [1]–[2], because of its complicated epitaxial material and extremely scaled process line width. GaAs Schottky diode has been evolved and applied in terahertz multiplexing, mixing and direct detection for decades, and still maintain unshakable, due to its high electron mobility, simple device structure, and small junction capacity, especially in the range from 1THz to 5THz [3]–[4].